Polarizable ferroelectric ceramic composition



Sept. 2, 1969 HISAO BANNO ET AL 3,464,924

POLARIZABLE FERROELECTRIC CERAMIC COMPOSITION Filed May 22, 1967 $6 With aclzlihon. of l.5wb%0f BizOa 4: 0 e", O Y i? 5 0 with addition. 0; L5 [110% Of Bigoi 3 40 and 0.75 urt.%0f' MM); 5 g 30- 73 20 5 g l0 3 a 0 l 1 I0 I00 I000 [0000 fine after olarization, Hours 0% Time after polqnzution, Hours 5 IO 00 mp0 10000 g madam of Lswmo Biz0 -Z with addition of l.5wt%0f BL O M11075 k 2 3-4 3 with addition of LSuAC %0[ 51 03 with addition of LSwtZ 0? BizOa and 0.?5 wt. MnO

% increase in resonance frcqucnc fr m h,

I00 I000 [0000 Time after olarization. HouYS limited States Patent G US. Cl. 25262.9 9 Claims ABSTRACT OF THE DISCLOSURE A novel and useful polarizable ferroelectric ceramic composition for use in piezoelectric and electrostrictive ceramic article consisting essentially of Pb(Zr-Sn'Ti)O wherein a part of the lead is replaceable by elements selected from Group II of the Periodic Table and containing at least one element selected from the group of Nb, Ta, Bi and rare earth element, and further containing Mn.

This invention relates broadly to compositions of matter and articles of manufacture fabricated therefrom. More particularly, the invention pertains to novel ferroelectric ceramics susceptible of electrostatic polarization and exhibiting, when polarized, electromechanical transducing properties similar to the Well known piezoelectric effect. As a result of these properties, materials.

of the type to which the present invention pertains have come to be known and may hereinafter be referred to as piezoelectric ceramics. While the principal product contemplated by the invention is the matured and polar ized ceramic, as well as articles fabricated therefrom, it is to be understood that it also encompasses as intermediates the unreacted physical mixture of raw materials and the heat reaction product of such mixtures. Accordingly, the term ceramic compositions will be used herein to encompass and designate generically the cornposition of matter at all stages from the unreacted physlcal mixtures to the matured and polarized ceramic which is the ultimate product.

The feature that the ceramic of lead titanate zirconate represented by Pb(Zr Ti )O wherein x:0.1 to 0.6 shows piezoelectric and electrostrictive effect is disclosed in US. Letters Patent No, 2,708,244 to Bernard Jaffe. Moreover, lead titanate zirconate stannate represented by Pb(Zr Sn Ti )O wherein x=0.1 to 0.6, y= to 0.9, z=0 to 0.65, x+y+z=1.0, derived from the basic composition represented by Pb(ZrTi)O shows also an excellent piezoelectric and electrostrictive effect is disclosed in US. Letters Patent No. 2,849,409 to Iaffe et al.

Furthermore, the feature that the above mentioned basic composition represented by Pb(Zr-Ti)O as well as Pb (Zr-Sn-Ti)O and Pb(Sn-Ti)O both derived from the basic composition wherein up to 30 atom percent of Pb is replaced by at least one element selected from the GroupII of the Periodic Table consisting of Sr, Ca, Ba, Cd, Zn, etc, such, for example, as (Pb-Sr) (Zr-T90 (Pb-Sr-Ca) (Zr-Ti)O (Pb-Ba) (Zr-Sn-TUO etc. show improved electromechanical coupling coeificient and dielectric constant is disclosed in US. Letters Patent Nos. 2,906,710 and 3,144,411 to Kulcsar et al., Japanese Patent No. 288,202 to Ikeda and British Patent No. 953,408.

Another feature that addition of at least one oxide selected from the oxides of Nb, Ta, and the rare earth elements including Y but excluding Ce as asecond in gredient to the above mentioned basic compositions makes Patented Sept. 2, 1969 it possible to increase the electromechanical coupling coefiicient and dielectric constant and also improve time stability is disclosed in US. Letters Patent No. 2,911,370 to Kulcsar.

It has also been disclosed in US. Letters Patent No. 3,117,094 to Roup et al. and Japanese Patent No. 301,176 to Marutake et al. that the similar effect can be obtained by addition of an oxide of Bi.

Thus, lead titanate zirconate stannate system ceramics if added with oxides of Nb, Ta, Bi, and the rare earth elements including Y but excluding Ce are transformed from hard material into soft material having a small coercive field and easily capable of effecting saturated polarization at a lower polarization potential and thus susceptable of piezoelectric characteristics. These lead titanate zirconate stannate system ceramics are widely used as a passive element such as a phonograph pickup element, a ceramic microphone element etc. However, the piezoelectric ceramics having the above mentioned compositions have small coercive field so that they are liable to lose polarity thereof when used as an active element adapted to cause displacement by supplied potential such as a speaker, a piezoelectric relay, an ultrasonic transducer etc. or as a passive element such as a piezoelectric ignitor element for generating a high potential. Thus, the piezoelectric ceramics having the above mentioned compositions have disadvantages that use thereof is limited to a comparatively low potential element.

The principal object of the invention is to obviate such disadvantages and provide a novel and useful polarizable ferroelectric ceramic composition having a comparatively high electromechanical coupling coeflicient and high coercive field and highly suitable for use as an active element such as a speaker, a piezoelectric relay etc. or as a piezoelectric ignitor element.

Another object is to provide a ferroelectric ceramic composition having an improved piezoelectric ceramic composition an improved piezoelectric characteristics and improved time stability.

A feature of t heinvention is the provision of such improved ferroelectric ceramic composition which consists essentially of a first basic ingredient of lead titanate zirconate, lead titanate zirconate stannate or those wherein up to 30 atom percent of Pb is replaced by at least one element selected from Group II of the Periodic Table consisting of Ca, Sr, Ba, Zn and Cd, and added with 0.1 to 10 weight percent of at least one oxide selected from the group of oxides of Nb, Ta, Bi, and the rare earth elements including Y and excluding Ce as a second ingredient and also added with 0.05 to 5 Weight percent of oxide of Mn as a third ingredient, and which has a comparatively high piezoelectric property and high coercive field without giving bad influence upon the electromechanical coupling coefficient, thereby obviating the above mentioned disadvantages of the soft material.

For a better understanding of the invention, reference is taken to the accompanying drawings which illustrate characteristics of ceramic bodiesaccording to the invention comprising a basic composition consisting of lead titanate zirconate compound and added with bismuth oxide and manganese dioxide, in which:

FIG. 1 is a diagram illustrating aging characteristic of electromechanical coupling coefiicient Kp;

FIG. 2 is a diagram illustrating aging characteristic of 3 EXAMPLE 1 PbO, TiO and ZrO were admixed in amount such that a basic composition represented by and a basic composition represented by 'o.5o' 0.5o) 3 were obtained. These basic compositions were added with 1.5 weight percent of Bi O with or without 0.75 weight i percent of MnO and the compositions thus obtained were mixed, ground, molded and calcined at a temperature ,of 700 to l,000 C. The reaction product thus obtained was ground again, molded and matured in PbO atmosphere at a temperature of 1,100 to l,300 C. to

obtain a disk shaped sintered product having a dimension of about 20 mm. dia. x 0.8 mm. thickness.

Both surfaces of the disk thus obtained were electroded. Then, the disk was polarized by applying a direct current electric field of 40 kv./cin. at a temperature of 80 C. for about 30 minutes and stored in the air at room temperature for one week. The electromechanical coupling coefficient Kp and coercive field E of the disk thus treated were measured and the results thereof were shown in the following Table 1.

TABLE 1 Electromechanical Addition coupling Coercive (wt, percent) coefficient field Sample Kp Ee No. Basic composition B120 MnOz (percent) (kv./crn.)

TABLE 3 Electromechanical Addition, coupling Coercive wt. percent coefiicient field 5 Sample Basic 4 Kp Ec No. composition B1203 MnOz (percent) (kv./cm.)

7A Pl)(ZI0 g-Tlo,i)03 2 0 28 5.3 7B Pb(ZIo.9-Tio.i)03 2 l 26 14.2 82L Pb(Zio s-Tig.2)0:r 2 O 30 6.3 8B. Pb(ZI"0.3-Tig,2)03 2 1 27 15.4 9A Pb(Zl'u,7-Tig 3)03 2 0 32 6.8 9B Pb(ZIo.7-Tio, )O3 2 l 31 16.0 10A. 1 Pb(ZI0.5-Tl0 4)03 2 0 42 7.3 1OB Pb(Z10.s-Tio.-i)O 2 1 39 17.2 11A Pb(Zi 5-Tin.5)O3 2 0 54 13. 9 11B Pb(Zl0,5-Tl0,5)03 2 1 54 22.3 12A Pb(ZI0,4-Tlgj)03 2 O 33 14.3 15 12B Pb(ZTQA-Tlfl fi 03. 2 1 v 23.4

EXAMPLE 4 The basic composition represented by 20 was added with Ta O and MnO in weight ratio of Ta O :MnO =2: 1, while the same basic composition was 29 added with Ta O only. These compositions thus obtained were treated under the same conditions as those in Example l to obtain ceramic disks. The electromechanical coupling coefiicient Kp' and coercive field E0 of the disks thus obtained were measured and the results thereof were *These samples 4A and 413 were the same as those shown in the Table 2 of the Example 2 and were shown for. the sake of comparison with the other samples in the above Table 4.

TABLE 2 Electromechanical Coercive coupling Sample coefilcieiit E0 No. Basic composition Addition Kp (percent) (km/cm.)

3A Pb(Z1'0.5a-Tlo.47)03..... 1.5 wt. percent Nb2O5 59 6 3B Pb(Zr@, ;-Tiu.n) O3 1.5 wt. percent NbzOs plus 16 0.75 wt. percent MnOz. 4A Pb(ZTo.55'Tl0,47) 0 1.5 wt. percent TazO5 61 9 4B Pb(Z1'0.5-3-T1u,47)03".-. 1.5 wt. percent TagOs plus 57 20 0.75 wt. percent MnOz. 5A Pb(Zro.aa-Tin.n)0; 1.5 wt. percent L320; 59 4 513 Pb(Zro.5s-Tio.47)Oa 1.5 wt. percent 11320.; plus 58 12 0.75 wt. percent MnOz. 6A Pl)(Zlo.5 -Tio.47)O 1.5 Wt. percent SnnO 57 5 6B Ib(Zi'0.53-Ti .n)O3 1.5 wt. percent SmzO; plus 56 0.75 wt. percent MnOz.

EXAMPLE 3 The basic composition represented by Pb(Zr -Ti, )O was added with 2 weight percent of Bi O with or without 1 weight percent of MnO The compositions thus obtained were treated under the same conditions as those in the Example 1 to obtain ceramic-disks. The electro mechanical coupling coefiicient Kp and coercive field Ec of the disks thus obtained were measured and the results thereof were shown in the following Table 3.

EXAMPLE 5 The basic compositions wherein a part (if Pb thereof was replaced by Sr, Ca, Cd, Zn were added with B1203 or Nb O with or without MnO The compositions thus obtained were treated under the same conditions as those in the Example 1 to obtain ceramic disks. The electromechanical coupling coefficient Kp and coercive field Ec F of the disks thus obtained were measured and the results thereof were shown in the following Table 5.

TABLE 5 Electromechanical Coercive Addition, wt. percent coupling field coefficient Ec Sample No. Basie composition Bigos Nb205 MIlOe Kp(pcrcent) (km/cm.)

24B (Planes-Stone)area-T103003 0 2 0-5 60 20.0

As can be seen from the Examples 1 to 7, the composi- EXAMPLE 6 tion added with MnO according to the invention renders The basic compositions represented by it possible to remarkably improve the coercive field with- Pb B Z 0 out substantially reducing the electromechanical coupling r055" 1M5) 3 2O coefiicient thereof if compared with those without addiwherein a part of Pb of the basic composition represented by Pb(Zr -Ti )O was replaced by Ba were added with 2 weight percent of Bi O with or without 1 weight percent of MnO The compositions thus obtained were treated under the same conditions as those in the Example 25 1 to obtain ceramic discs. The electromechanical coupling coefiicient Kp and coercive field E0 of the disks thus treated were measured and the results thereof were shown in the following Table 6.

tion of MnO and, particularly, make the coercive field of the former about twice and maximum thrice that of the latter.

EXAMPLE 8 The basic composition represented by was added with 1.5 weight percent of Bi O with or without 0.75 weight percent of MnO The compositions thus TABLE 6 Electromechanical Addition, coupling Coercive wt. percent coctllfield Sample cient Kp Ec No. Basic composition B003 MnOz (percent) (kw/cm.) Pb (ZXoea-TioAs} O3 0 0 55 7.8 26A (Pbo.ta-Bau,u )(Zr0 $104903 2 0 57 8.3 (Phone-Baum) 2 1 54 14.3 H (Phase- 1010) 2 0 58 8.5 (Pbono- 2 1 55 15.4 (Pboss- 2 0 57 8.3 P1505543 2 1 5s 16. 3 (Pbolso-Bfio. 2 U 54 9.0 (Phase-Baa 2 1 53 17.2 15-1380. 2 0 so 10. 0 Pbo.1sBao. 2 1 50 14. 3

EXAMPLE 7 obtained were treated under the same conditlons as those The basic composltlons represented by In the Example 1 to obtain ceramu: disks. The disks thus treated were stored in the air at room temperature and Pb(Zr -Sn -T1 )0 the aglng characteristics of the electromechanical coupling were added with 2 weight percent of Bi O with or without 1 weight percent of MnO The compositions thus obtained were treated under the same conditions as those in the Example 1 to obtain ceramic disks. The electromechanical coupling coefiicient Kp and ceramic field Ec of the disks thus treated were measured and the results thereof were shown in the following Table 7.

coefiicient Kp, dielectric constant e and resonance frequency Fr thereof were measured and the results thereof were shown in FIGS. 1 to 3. As can be seen from these drawings, the aging characteristics of the basic compositions added with 1.5 weight percent of Bi O and 0.75 weight percent of MnO were extremely slight in variation if compared with those of the basic composition added TABLE 7 Electromechanical Addition, coupling Coercive wt. percent coctlifield Sample cicnt Kp Ec No. Basic composition B: MnOz (percent) (kvJem 31A Pl)(Z1'o.45-Sn Tio.-is)O3 2 0 52 8. 3 31B Pl)(Zr rSnmn-Tia.45)03.. 2 1 50 16. 3 32A Pb(Zl'o g-Silum-Tim )O3 2 U 52 8. 5 32B Pl)(Zl'o.35-sn0.:o-Tl0.45)03 2 1 51 17. 4 33A Pl)(Zlo z5-Sl'lu.30-Tio 45)O3 2 [l 53 8. 6 33B Pl)(Zlogs-SllosrTlOAi)O3 2 1 49 18. 3 34A Pl)(Zlu 15-Sll0 4o-Tl0.-15)03 2 U 52 9. 0 34B Pl)(zlo ysllugn-Tio )O 2 1 48 19. 3 35A Pl)(Zla,ga-snu w'riodfloa. 2 O 50 10. 1 35B Pb(Zlo.oa-Sn0.5c-Tiu.qs)O 2 1 45 18. 4

with 1.5 weight per cent of B1 only, which showed the advantageous effect of MnO In carrying out the invention into effect, at least one element selected from the group consisting of Nb, Ta, Bi and the rare earth elements including Y but excluding Ce to be added as the second ingredient and Mn to be added as the third ingredient may be added in the form of powder or of various kinds of compounds including the other elements. The second ingredient must be added in an aggregate quantity equivalent to from 0.1 to weight percent of respective oxide, while the third ingredient must be added in an aggregate quantity equivalent to from 0.05 to 5.0 weight percent of manganese dioxide. The reason why the lower limits of the second and third ingredients are limited to 0.1 weight percent and 0.05 weight percent, respectively, is as follows. These ingredients serve to act sensitively even if they are added in an extremely small amount. 0.1 weight percent of the second ingredient and 005 Weight percent of the third ingredient are sufficient to obtain the advantageous effects thereof. While, the reason why the upper limits of the second and third ingredients are limited to 10.0 weight percent and 5.0 weight percent, respectively, is as follows. Addition of more than the above upper limits causes a remarkable decrease of the electromechanical coupling coeflicient of the ceramic composition. It is preferable to use from 0.5 to 5.0 weight percent of the second ingredient and from 0.25 to 2.5 weight percent of the third ingredient for the purpose of improving the electromechanical coupling coefiicient of the ceramic composition.

The reason why the values of x, y and z of derived from the former are limited to x:0.l to 0.6,

y=0 to 0.9, 23:0 to 0.65 and x+y+z:l.0 is that the basic compositions limited in the above range show a practically available values of the electromechanical coupling coefficient and remarkably improve the coercive field of the basic compositions.

The reason why the amount of Pb of the basic composition represented by Pb(ZrTi)O or Pb(ZrSnTi)O to be replaced by at least one element selected from Group II of the Periodic Table is limited to up to 30 atom percent is that such amount of Pb to be replaced has been formed as the upper limit thereof in order to obtain the practically desirable value of the electromechanical coupling coefficient.

As above mentioned, the invention that lead titanate zirconate system ceramic composition consisting of lead titanate zirconate, lead titanate zirconate stannate or those zirconate and stannate in which a part of the lead is replaced by Ba, Ca, Sr, Cd, Zn, etc. is added as the second ingredient with at least one oxide of Nb, Ta, Bi, and the rare earth elements including Y but excluding cerium, and

added as the third ingredient with Mn0 ensures an extremely good time stabilities with only slightly decreasing the electromechanical coupling coefficient Kp but without departing from the practical range thereof and further provides the important advantage that coercive field Ec is remarkably improved. Thus, the lead titanate zirconate system ceramic composition according to the invention can be applied effectively to the fabrication of" elements adapted to cause displacement by supplied po'ten tial such as a speaker, a piezoelectric relay, an ultrasonic transducer, etc. and a piezoelectric ignitor element for generating high voltage etc.

What we claim is:

f. A polarizable ferroelectric ceramic composition consisting essentially of a compound represented by the formula selected from Pb(Zr -Ti 0 wherein x=0.l to

0.6, and Pb(Zr Sn -Ti, )O wherein x =O.1-to 0.6, y=0 to 0.9, 1 :0 to 0.65 and x+y+z=l.0, and containing at least one element selected from the group consisting of niobium, tantalum, bismuth, and the rare earth elements including yttrium but excluding cerium in an aggregate quantity equivalent to from 0.1 to 10.0 weight percent of respective oxide, and further containing manganese in an aggregate quantity equivalent to from 0.05 to 5.0 weight percent of manganese dioxide.

2. A polarizable ferroelectric ceramic composition as claimed in claim 1 wherein up to 30 atom percent of the lead is replaced by at least one element selected from Group II of the Periodic Table consisting of calcium, strontium, barium, zinc and cadmium.

3. A polarizable ferroelectric ceramic composition consisting essentially of a compound represented by the formula selected from Pb(Zr Ti )O wherein x:0.l to 0.6, and Pb(Zr -Sn -Ti )O wherein x=0.l to 0.6, y=0 to 0.9, z=0 to 0.65 and x+y+z=l.0, and containing at least one element selected from the group consisting of niobium, tantalum, bismuth, and the rare earth elements including yttrium but excluding cerium in an aggregate quantity equivalent to from 0.5 to 5.0% by weight of respective oxide and further containing manganese in an aggregate quantity equivalent to from 0.25 to 2.5% by weight of manganese dioxide.

4. A polarizable ferroelectric ceramic composition as claimed in claim 3 wherein up to 30 atom percent of the lead is replaced by at least one element selected from Group II of the Periodic Table consisting of calcium, strontium, barium, zinc and cadmium.

5. An electrically polarized ceramic body consisting essentially of a compound represented by the formula selected from wherein x:0.l to 0.6, 3 :0 to 0.9, 21:0 to 0.65 and x+y+z=1.0, and containing niobium in an aggregate quantity equivalent to from 0.5 to 5.0 weight percent of Nb O and further containing manganese in an aggregate quantity equivalent to from 0.25 to 2.5 weight percent of M1102.

6. An electrically polarized ceramic body as claimed in claim 5, wherein up to 30 atom percent of the lead is replaced by strontium.

7. An electrically polarized ceramic body consisting essentially of a compound represented by the formula wherein x=0.l to 0.6, 3 :0 to 0.9, z=0 to 0.65 and x+y+z=l.0, and containing tantalum in an aggregate quantity equivalent to from 0.5 to 5.0 Weight percent of Ta O and further containing manganese in an aggregate quantity equivalent to from 0.25 to 2.5 weight percent of M002.

8. An electrically polarized ceramic body consisting essentially of a compound represented by the formula wherein x=0.l to 0.6, y:0 to 0.9, z:0 to 0.65 and x +y+z=l.0, and containing bismuth in an aggregate quantity equivalent to from 0.5 to 5.0 weight percent of Bi O and further containing manganese in an aggregate quantity equivalent to from 0.25 to 2.5 weight percent of M1102;

9 10 9. An electrically polarized ceramic body as claimed in FOREIGN PATENTS claim 8 wherein up to 30 atom percent of the lead is re- 1,463,876 12/1966 France placed y barium- 1,462,270 12/1966 France.

References Cited 5 TOBIAS E. LEVOW, Primary Examiner UNITED STATES PATENTS J. COOPER, Assistant Examiner 3,117,094 1/1964 Roup et al. 252-629 US. Cl. X.R.

3,372,121 3/1968 Banno 252 -62 9 106-39 UNITED 'STA IES PATENT" OFFICE CERTIFICATE OF 'COZRRECTION Patent No. 3,464,924 September 2, 1969 Hisao Banno et al I It is certified that error. appears in the above identified patent and that said Letters Patent vare hereby corrected as shown below:

Column 2, line 15, "susceptable" should read susceptible Columns 5 and 6 TABLE 5 fifth column, line 6 thereof, "0" should read 1 same TABLE 5 sixth column, line 6 thereof,

"52" should read 5O Column 5 line 26, "discs" should read disks Columns 5 and 6 TABLE 7 sixth column, line 10 thereof, "18.4" should read 18.3

Signed and sealed this 10th day of November 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

